The field of the present invention is lighting apparatus providing selectively varying wavelengths of light.
Ultraviolet light is electromagnetic radiation in the region of the spectrum located between X-rays and visible light. It is divided into three principal ranges: (1) UV-A, or longwave, (2) UV-B, or mid-range, and (3) UV-C, or shortwave. For each of these UV ranges, specific applications have been developed for its use and new applications are continuously being developed.
To obtain a desired ultraviolet wavelength, the fluorescent tube is most commonly used. The fluorescent tube is an electric discharge device that uses a low pressure mercury vapor arc to generate ultraviolet energy. The ultraviolet energy released in typical, commercially available fluorescent tubes is primarily at the wavelength of about 294 nanometers. In general, this ultraviolet energy is converted into other ultraviolet wavelengths by the use of phosphors which have the ability to absorb the ultraviolet energy and re-radiate it in other wavelengths. For example, longwave ultraviolet of about 365 nanometers and mid-range ultraviolet of about 300 nanometers are created by coating the inside of the fluorescent tubes with the proper phosphor(s) which converts the shortwave ultraviolet. The envelope of the tube is also typically made of a glass that inhibits the passage of the shortwave ultraviolet. To obtain a shortwave ultraviolet tube, a special glass which transmits about 254 nanometers is generally used, and no phosphor is required.
A common tool of those engaged in DNA research is the ultraviolet transilluminator. These devices provide up to three ultraviolet light sources to irradiate and/or visualize DNA patterns contained in gel matrices. Most commonly, transilluminators comprise a single set of ultraviolet lamps emitting one selected wavelength. In most such research, three separate wavelengths are used. Thus, it is common to use multiple such units in this work. At times, it may also be of value to employ a white light or other spectral selections such as, for example, the 420 nm and the 480 nm regions.
A conventional transilluminator having a single UV wavelength is disclosed in U.S. Pat. No. 4,657,655, incorporated herein by reference. An ultraviolet light apparatus having multiple wavelengths accomplished by rotation of a tube mounting mechanism is disclosed in U.S. Pat. No. 5,175,437, incorporated herein by reference.